1. Technical Field
The present invention relates to a technique for converting an image having pixels whose colors are expressed based on light's three primary colors to an image having pixels whose colors are expressed based on basic printer colors.
2. Related Art
With the recent rapid increase in popularity of digital cameras, users have turned to a convenient technique referred to as “photo-printing” for obtaining output copies of their images. According to this technique, an electrophotographic image forming device such as a printer is used for recording an image on a recording medium, such as a paper.
Electrophotographic image forming devices have been generally used for outputting text images or line drawing images. However, different to such images, those taken by digital cameras contain delicately varying hues that impart a so-called “natural” quality to an image to produce a “natural image”. It is known that, when an electrophotographic image forming device prints out a “natural image”, pseudo or false contours (hereafter, “tone jumps”) may appear, as shown in FIGS. 8A and 8B. This effect is pronounced when an image recording medium is a printing paper for photo-printing use. FIG. 8B, which is a cyan color image of the image shown in FIG. 8A, shows prominent tone jumps.
There have heretofore been proposed a number of techniques for avoiding generation of tone jumps.